A coordinate measuring device is well-known from prior art. See, for example, the lecture script “Pattern Placement Metrology for Mask Making” by Dr. Carola Bläsing. The lecture was given on the occasion of the Semicon conference, Education Program, in Geneva on Mar. 31, 1998, and describes the coordinate measuring machine in detail. The structure of a coordinate measuring machine, as it is known, for example, from prior art, will be explained in more detail in the following description associated with FIG. 1. A method and a measuring device for determining the position of structures on a substrate is known from German published application DE 100 47 211 A1. For details on the mentioned position determination, see that document.
German patent document DE 199 49 019 C2 discloses a measuring device for measuring structures on substrates varying in thickness. The substrates are inserted in an X/Y slide. The X/Y slide comprises a peripheral rim. The measuring device itself is equipped with illumination optics, wherein there are provided several compensation elements needed for compensating the optical path length. These compensation elements are selected corresponding to the substrate to be measured. The compensation elements are located in storage compartments on the peripheral rim of the recess of the X/Y slide. Depending on which compensation element is needed, they are removed from the storage compartment by means of the illumination optics. In this way, an equal optical thickness of the whole system consisting of compensation element and substrate is achieved irrespective of the mechanical thickness of the substrate used. One disadvantage is that the compensation elements merely rest on the illumination optics and may thus constitute a further error source, which may result in faulty measurements with the measuring device.
Document DE 100 31 719 discloses an illumination means having a light source, an optical fiber bundle, a coupling-in optical system upstream of and a coupling-out optical system downstream of the fiber bundle, and an illuminating optical system. A homogenizing optical system between the coupling-out optical system and the illuminating optical system effects a homogenization of the intensity distribution in the image field. The homogenizing optical system consists of a microhoneycomb condenser and a lens member, which superimpose the exit opening of the fiber bundle in an intermediate image plane to form a homogeneous intermediate image. The coordinate measuring device itself includes an X/Y measurement table to receive a substrate having a structure to be measured, and the illumination system mentioned above.
Document DE 198 58 428 discloses a movable x/y measurement table having two measurement mirrors, which are arranged to be orthogonal to each other, for interferometric position determination. The movable measurement table, a mirror body carrying the measurement mirrors, and the receptacle for the substrate (9) are implemented as separate elements.